The family of James Foley, a Boston-based foreign correspondent who was abducted in Libya in 2011, said Wednesday that he was kidnapped again on Thanksgiving Day, this time while reporting from Syria, and remains missing.

Foley was reportedly taken by unidentified gunmen in the northwest of the country, his family said, an area with heavy fighting and high death tolls in the ongoing conflict. Foley’s family initially had asked that the kidnapping not be disclosed, but decided to make his capture public in an appeal for his release.

“We want Jim to come safely home, or at least we need to speak with him to know he’s OK,” John Foley, father of James Foley, said in a statement. “Jim is an objective journalist and we appeal for the release of Jim unharmed. To the people who have Jim, please contact us so we can work together toward his release.”

The statement was posted on a website,freejamesfoley.org, created to publicize the campaign for Foley’s release. A Facebook page and Twitter account were also created, and news organizations that Foley has worked for echoed the family’s calls.

Michael Foley, James Foley’s brother, said the family had kept his capture a close secret for weeks as they waited for his release. But with little sign of progress, they decided it was time to make a public appeal.

He described his brother as an “extremely cautious” reporter who felt a sense of duty to document the plight of war-torn countries.

James Foley’s parents have scheduled a news conference Thursday at their New Hampshire home.

Colleagues of Foley describe him as a brave and dedicated reporter who was fiercely committed to documenting the conflict and its impact on civilians.

Foley, 39, was reporting on the Syrian civil war from Idlib Province, the scene of fierce fighting between government and rebel forces.

No group has claimed responsibility for taking Foley, and there have been no reports of his whereabouts. Syria has banned almost all foreign journalists from the country, and specialists said Foley’s capture underscores the dangers correspondents face there.

At least 28 journalists were killed in Syria last year, and kidnappings have become more common.

“In the past year, it’s been the deadliest country in the world” for news media, said Sherif Mansour of the Committee to Protect Journalists, a nonprofit group that promotes press freedom.

Foley, a Marquette University graduate, has reported on conflicts in Afghanistan, Iraq, and Libya, where he was taken captive in April 2011 by forces loyal to Libya’s leader, Moammar Khadafy, while on assignment for GlobalPost, a Boston-based international news organization.

Foley and two other journalists spent 44 days in Libyan prisons before being released, the organization said. Foley later returned to the country to cover the overthrow of the Khadafy regime.

On Thanksgiving Day, Foley was traveling toward the Turkish border when he was intercepted by an unmarked car, according to a GlobalPost story posted on Wednesday.

A Syrian witness later recounted that armed men forced Foley from his vehicle, the story stated.

“The witness said he noticed nothing that would indicate whether the aggressors were rebel fighters, individuals looking for a ransom, members of a progovernment militia, or a religious-based group with other motivations,” the organization reported.

GlobalPost’s chief executive, Philip S. Balboni, said the organization has been “working intensively” over the past six weeks with parties in the United States and the Middle East to secure Foley’s freedom.

“Jim is a brave and dedicated reporter who has spent much of the past year covering the civil war in Syria, believing like so many of his colleagues that this is a very important story for the American people to know more about,” he said in a statement. “We urge his captors to release him.”

The GlobalPost report said it was unclear whether Foley had been seized by the same group that captured an NBC News correspondent, Richard Engel, last month. Engel and three members of his team, who were abducted in the same region as Foley, were held captive for five days.

Foley was recently working for the French news service, Agence France-Presse, which said in a statement it was “taking every measure in our power to facilitate his release.”

“James is a professional journalist who has remained totally neutral in this conflict,” said Emmanuel Hoog, chief executive of the news service. “His captors, whoever they may be, must release him immediately.”

The news service said it had remained in close contact with Foley’s family and friends, but that there had been no news of his whereabouts.

Foley’s work has “considerably enriched” coverage of the Syrian conflict, the organization said. Since March 2012, Foley had provided about 30 video reports, it said.

At least 67 journalists were killed worldwide while reporting in 2012, a 42 percent increase over 2011, according to the Committee to Protect Journalists.

Mansour, the group’s Middle East and North Africa coordinator, said reporters have “smuggled themselves into the country” to report on the fighting in Syria. Both government and rebel forces have abducted journalists, he said.

Mansour said the family’s decision to publicize Foley’s capture rests on the hope that media attention and public pressure will lead to a breakthrough. “We are still hopeful,” he said.

In a column last year for a field guide for GlobalPost correspondents, Foley described the “harrowing experience” of ­being captured in Libya.

“I saw a colleague killed. My family was thrown into a world of constant worry. The news organization I work for was thrust into a situation of working around the clock on my behalf,” he wrote.

Yet seven months later, he returned to Libya.

“It’s good to be back,” he wrote. “This story matters, and I wanted to be here telling it from the frontlines.”